Method and apparatus for quick paging in a wireless communication system

ABSTRACT

Method and apparatus for pseudo-synchronized paging to a mobile station in a wireless communication system. A number of paging repetitions is assigned, wherein a quick page message is repeatedly sent to a target mobile station for the number of paging repetitions. The number of paging repetitions is part of a paging instruction from a base station controller to a base station. The pseudo-synchronized method is used when the target mobile station is soft handoff.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional U.S. Application Ser.No. 60/261,454, entitled “METHOD AND APPARATUS FOR SYNCHRONIZATION OFQPCH SOFT HANDOFF,” filed Jan. 12, 2001, which is incorporated herein byreference in its entirety for all purposes.

Reference To Co-Pending Application For Patent

The present invention is related to a co-pending U.S. Application forPatent entitled “CELLULAR COMMUNICATION SYSTEM WITH COMMON CHANNEL SOFTHANDOFF AND ASSOCIATED METHOD,” by Edward G. Tiedemann, Jr. et al.,having U.S. application Ser. No. 09/727,712, filed Nov. 30, 2000 andassigned to the assignee hereof.

BACKGROUND

1. Field

The present invention relates to communications systems. Specifically,the present invention relates to methods of providing quick pages in awireless communication system.

2. Background

In a wireless communications system a base station pages a mobilestation indicating that a call is pending. The paging signal istransmitted on a separate channel, referred to as a paging channel.While the paging channel may be implemented on a separate carrierfrequency, in a spread spectrum system, such as a Code Division MultipleAccess, CDMA, type system, a unique code is applied to paging messages,thus providing a paging channel.

The base station generates pages in response to instructions receivedfrom a Base Station Controller, BSC. In one embodiment, the BSC alsoinstructs the base station to send a Quick Page, QP, signal. The OPsignal is transmitted on a separate Quick Page Channel, QPCH. The quickpage message may be one bit or may be a message made up of multiplebits.

A problem exists in generating QP messages when a mobile station is insoft handoff. During soft handoff, the BSC instructs those base stationsin a neighborhood around the mobile station to transmit a QP message.After sending the QP message, each base station is instructed to pagethe mobile station. For each base station, the mobile station has anassigned paging slot. The loading of the base stations in theneighborhood may prevent one or all of the base stations from sendingthe corresponding page during the assigned paging slot. Therefore, thereis a need for a method of providing quick pages while a mobile stationis in soft handoff.

SUMMARY

According to one aspect, in a wireless communication system having abase station controller and a plurality of base stations, a methodincludes receiving a paging instruction from the base station controllerat a base station of the plurality of base stations, the paginginstruction specifying a number of paging repetitions; and transmittinga quick paging message to a target recipient of the paging instructionfor the number of paging repetitions.

According to another aspect, in a wireless communication system having abase station controller and a plurality of base stations, a base stationincludes means for receiving a paging instruction from the base stationcontroller at a base station of the plurality of base stations, thepaging instruction specifying a number of paging repetitions, and meansfor transmitting a quick paging message to a target recipient of thepaging instruction for the number of paging repetitions. In stillanother aspect, in a wireless communication system having a base stationcontroller and a plurality of base stations, a mobile station includes ameans for receiving a plurality of quick paging messages from theplurality of base stations, a means for receiving a first paging messagefrom a first of the plurality of base stations, a means for receiving asecond paging message from a second of the plurality of base stations,and a means for responding to at least one of the first and secondpaging messages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a portion of a wireless communication system.

FIG. 2 is a portion of a wireless communication system.

FIG. 3 is a timing diagram of a quick paging protocol.

FIGS. 4A and 4B are timing diagrams of quick paging protocols duringsoft handoff.

FIG. 5 is a flow diagram of quick paging control during soft handoff.

FIG. 6 is a base station supporting a quick paging protocol.

DETAILED DESCRIPTION

The word “exemplary” is used exclusively herein to mean “serving as anexample, instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

In a spread spectrum system, such as a Code Division Multiple Access,CDMA, communications system, signals are spread over a wide bandwidthvia the use of a code, such as a Pseudorandom Noise, PN, spreadingsequence. The “TIA/EIA/IS-95 Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System,”hereinafter referred to as “the IS-95 standard,” and the“TIA/EIA/IS-2000 Standards for cdma2000 Spread Spectrum Systems,”hereinafter referred to as “the cdma2000 standard,” detail spreadspectrum CDMA systems. Further, operation of a CDMA system is describedin U.S. Pat. No. 4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESSCOMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” assignedto the assignee of the present application for patent and herebyexpressly incorporated by reference.

In one embodiment, such as a communication system consistent with thecdma2000 standard, a Quick Paging Channel, QPCH, is used to alert mobilestations to receive paging information, such as transmitted on a ForwardCommon Control Channel, F-CCCH or a Paging Channel, PCH.

FIG. 1 is a diagram of a communications system 100 that supports anumber of users and is capable of implementing at least some aspects andembodiments of the invention. System 100 provides communication for anumber of cells 102A through 102G, each of which is serviced by acorresponding base station 104A through 104G, respectively. In theexemplary embodiment, some of base stations 104 have multiple receiveantennas and others have only one receive antenna. Similarly, some ofbase stations 104 have multiple transmit antennas, and others havesingle transmit antennas. There are no restrictions on the combinationsof transmit antennas and receive antennas. Therefore, it is possible fora base station 104 to have multiple transmit antennas and a singlereceive antenna, or to have multiple receive antennas and a singletransmit antenna, or to have both single or multiple transmit andreceive antennas.

Terminals 106 in the coverage area may be fixed (i.e., stationary) ormobile. As shown in FIG. 1, various terminals 106 are dispersedthroughout the system. Each terminal 106 communicates with at least oneand possibly more base stations 104 on the downlink and uplink at anygiven moment depending on, for example, whether soft handoff is employedor whether the terminal is designed and operated to (concurrently orsequentially) receive multiple transmissions from multiple basestations. Soft handoff in CDMA communications systems is well known inthe art and is described in detail in U.S. Pat. No. 5,101,501, entitled“METHOD AND SYSTEM FOR PROVIDING A SOFT HANDOFF IN A CDMA CELLULARTELEPHONE SYSTEM”, which is assigned to the assignee of the presentinvention and incorporated by reference herein.

The downlink refers to transmission from the base station to theterminal, and the uplink refers to transmission from the terminal to thebase station. In the exemplary embodiment, some of terminals 106 havemultiple receive antennas and others have only one receive antenna.Similarly, some of terminals 106 have multiple transmit antennas andothers have single transmit antennas. There are no restrictions on thecombinations of transmit antennas and receive antennas. Therefore, it ispossible for a terminal 106 to have multiple transmit antennas and asingle receive antenna or to have multiple receive antennas and a singletransmit antenna or to have both single or multiple transmit or receiveantennas. In FIG. 1, base station 104A transmits data to terminals 106Aand 106J on the downlink, base station 104B transmits data to terminals106B and 106J, base station 104C transmits data to terminal 106C, and soon.

FIG. 2 illustrates the neighborhood 130 around mobile station 106Aincluding cells 102A, 102B, 102C, 102D, and 102E. The mobile station106A is herein referred to as MS1. The neighborhood may be considered toinclude those base stations that are in range to communicate with mobilestation 106A. The neighborhood determination is made by the Base StationController, BSC 120. The BSC 120 controls operation of the base stationswithin system 100 and interfaces with a Public Switching TelephoneNetwork, PSTN, another wireless system, a data link, such as theInternet, or any of a variety of other access networks.

FIG. 3 illustrates generation of Quick Paging, QP, messages in awireless system 100. On a pending communication request for MS1, the BSC120 generates an instruction to page MS1 and specifically to provide aQP message to MS1. These instructions are provided to multiple basestations within neighborhood 130. Illustrated are BTS 102A and BTS 102Das examples, however, BSC 120 may transmit the instruction to any of anumber of base stations. The BSC 120 sends the instruction during theinterval of time t1 to t2. In response to the instruction, the BTSs 102Aand 102D generate a OP message during the interval of time t3 to t4. Inone embodiment, the QP message is a one bit message. The OP message issent on a QP channel, QPCH. Each of the base stations in theneighborhood 130 transmits a QP message during this interval. Subsequentto the QP message, each base station is instructed to send a page toMS1. As discussed hereinabove, this presents a problem as any one of thebase stations within the neighborhood 130 may be loaded, havinginsufficient resources to page the MS1. In this case, such a basestation may have to prioritize pages, or ignore the instruction from theBSC 120.

The MS1 receives the QP messages from the base stations in theneighborhood 130. The MS1 combines the QP messages, thus increasing thereliability of the information. Each base station that is not able, orchooses not to transmit the QP message to MS1 reduces the reliability ofthe message.

One embodiment solves this problem by implementing a mandatory scheme,wherein each base station in neighborhood 130 that receives theinstruction from BSC 120 is required to send a QP message followed by apage message regardless of the loading of the base stations.

An alternate embodiment provides repeated QP messages, allowing basestations multiple opportunities to send the page. Referring to FIG. 4A,again the BSC 120 has sent an instruction to BTSs 102A and 102D. Inresponse, both base stations send QP messages during the interval oftime t5 to t6. The instruction includes a number of retries, identifiedas N, wherein if N=1 a mandatory scheme is implemented. The paginginterval of each base station begins at time t7 and continues to timet10 Within the paging interval, a time slot is assigned to the MS1, andother time slots are assigned to other mobile stations. The time slotassigned to MS1 is from time t8 to time t9. As illustrated in FIG. 4A,the BTS 102D has hatching during the MS1 paging slot to indicatetransmission of the paging message during this slot. The loading of BTS102D allowed the transmission. In contrast, BTS 102A was loaded so as toprevent transmission of the paging message during the time slot assignedto MS1, i.e. from time t8 to time t9. At a subsequent time from t14 tot15, also assigned to MS1, BTS102D does not transmit the paging message,however, at this time BTS102A allows transmission of the paging message.In this way, BTS102D sent the paging message at a first time, whileBTS102A sent the paging message at a second time. According to oneembodiment, two slots are designated between time t7 and t10 (the secondslot is not shown) for paging messages. Similarly, two slots aredesignated between time t13 and t16 (the second slot is not shown) forpaging messages.

In an alternate embodiment, in response to the page message receivedfrom the BSC, each BTS calculates the available bandwidth fortransmission. If a BTS has bandwidth to transmit the paging message inthe next paging slot, the BTS sends a paging confirmation message to theBSC. The paging confirmation message identifies the transmitter as a BTSavailable to send the paging message to the MS during the next slot. Asillustrated in FIG. 4B, the BTS 102D receives the paging message fromthe BSC 120 and determines there is sufficient bandwidth available tosend the paging message to the target MS. Note that the BSC 120 alsoinstructs the BTSs to send quick paging messages N times. The BTS 102Dtransmits a paging confirmation message to the BSC 120 at timet_(page1). The BTS 102D then transmits a quick paging message during thetime interval t5 to t6 and the paging message during the time intervalt8 to t9. The BTS 102A also receives the paging message from the BSC 120but determines there is not sufficient bandwidth available to send thepaging message to the target MS. The BTS 102A transmits a quick pagingmessage during the time interval t5 to t6. The transmission bandwidth ofBTS102A changes subsequent to time t5 such that BTS 102A has sufficientbandwidth to transmit the paging message in a next slot. The BTS 102Asends a paging confirmation message to the BSC 120 at time t_(page2). Aquick paging message is sent from BTS 102A during the time interval fromt11 to t12. The BTS 102A then sends the paging message during the nextslot, i.e., time interval t14 to t15. The present embodiment allows eachBTS to send a paging message during one of multiple time intervals. TheBTS identifies each time interval during which the paging message issent to the target MS. In this way, for each BTS, the BSC 120 may tracktransmission of the paging message.

The BSC may use this information to modify a quick paging soft-handofflist maintained at the BSC, BTS and MS. According to one embodiment, theBSC ignores those BTS having insufficient bandwidth to transmit thepaging message, thus saving power consumption at the MS as the MS doesnot need to update the list as often.

One embodiment for implementing the quick paging described hereinaboveis illustrated in FIG. 5. The method 400 is performed in a base stationor other control terminal, wherein at step 402 the base station receivesa quick paging instruction for a given mobile station, MS1. Theinstruction also indicates a number of paging repetitions, identified asN. At step 404 the base station initializes a slot index i to the valueN. At decision diamond 406 the base station determines if the number ofpaging repetitions is equal to 1. For the case of N=1, the base stationsends the quick paging signal and then sends the page message in thefirst slot assigned to MS1, the target recipient of the page. Asindicated in FIG. 5, the base station sends the quick paging message forMS1 and then sends the paging message in slot i at step 408. For thecase of N=1, the paging is synchronized between all of the basestations, wherein each base station transmits the paging message duringa same slot assigned to the target mobile station.

In contrast, if the number of paging repetitions does not equal one,processing continues to step 404 to send the quick paging message forMS1. The case of N>1 is referred to as a pseudo-synchronized pagingscenario. At step 410 the base station determines the loading conditionfor pending transactions. If the paging slots available from the basestation are congested, the base station increments the slot index atstep 414. If the base station loading allows transmission of the page toMS1, then the page is sent during slot i at step 412. Processing thencontinues to step 414 to increment the slot index. At decision diamond416, the index i is compared to the number of paging repetitions N,wherein if the number of paging repetitions is satisfied, the processends. Else, processing returns to step 404 to send the quick pagemessage to MS1. Note in one embodiment, once the base station transmitsthe paging message the process for ends for the target mobile stationand no further quick page messages are sent.

FIG. 6 illustrates a base station operative within a wirelesscommunication system, adapted for implementing a pseudo-synchronizedmethod of paging as in FIG. 5. The base station 500 includes receivecircuitry 502 for processing received signals from a base stationcontroller (not shown). The receive circuitry 502 provides the number ofpaging repetitions N to the paging repetition counter 504. The counter504 is coupled to the paging unit 506 and a quick paging unit 508. Thecounter 504 provides the status of repetitions remaining for a paginginstruction associated with a target mobile station. The quick pagingunit 508 uses this information to determine the number of times to sendthe quick page message. The paging unit 508 receives loading andscheduling information from the loading determination unit 512. Theloading determination unit 512 is also coupled to the transmit circuitry510 and determines if the loading will allow a page to the targetrecipient. The quick paging unit 508 and the paging unit 506 providepaging information to the transmit circuitry 510. The quick paging unit508 initiates transmission of quick page messages for the number ofpaging repetitions as instructed by the base station controller (notshown).

In one embodiment, a mobile station operating within a wirelesscommunication system receives and processes the quick paging messagesfrom at least two base stations while in soft handoff. The mobilestation then receives and processes a first paging message from a firstbase station, wherein the first paging message is received during atransmission cycle of the first base station. During a subsequent cycle,the mobile station receives a second paging message from a second basestation. The mobile station then processes the paging information anddetermines a response with respect to the first and second basestations. The receiving and processing may be performed bycomputer-readable instructions stored in memory resident to the mobilestation. Also, the receiving and processing may be performed bydedicated hardware, firmware, or a combination thereof.

As disclosed hereinabove, a method for processing paging messages in awireless system allows for individual loading conditions of the basestations in communication with a mobile station. By designating a numberof paging repetitions, a base station is not prevented from sending apaging message due to loading, but rather may send the page when theloading allows it.

Thus a variety of methods have been illustrated hereinabove for pagingin a wireless system. Each method finds application according to thedesign and resource requirements of a given system. While the variousembodiments have been described with reference to a CDMA type spreadspectrum communication system, the concepts are applicable to alternatespread spectrum type systems, as well as other type communicationsystems. The methods and algorithms presented hereinabove may beimplemented in hardware, software, firmware, or a combination thereof.For example, using the MMSE approach to a non-time gated pilot, theequations for solving for the combiner weights may be performed insoftware or using a Digital Signal Processor, DSP, to perform thecalculations. Similarly, the adaptive algorithms may be implemented insoftware in the form of computer readable instructions stored on acomputer readable medium. A Central Processing Unit, such as a DSP core,operates to perform the instructions and provide signal estimates inresponse. Alternate embodiments may implement hardware, such as anApplication Specific Integrated Circuit, ASIC, where feasible.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill in the art would further appreciate that the variousillustrative logical blocks, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, circuits,and steps have been described above generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware depends upon the particular application and design constraintsimposed on the overall system. Skilled artisans may implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a Digital SignalProcessor (DSP), an Application Specific Integrated Circuit (ASIC), aField Programmable Gate Array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCDROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be an integral part of theprocessor. The processor and the storage medium may reside in an ASIC.The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. In a wireless communication system having a basestation controller and a plurality of base stations, a methodcomprising: receiving a paging instruction from the base stationcontroller at a base station of the plurality of base stations, thepaging instruction specifying a number of paging repetitions; andtransmitting a quick paging message to a target recipient of the paginginstruction for the number of paging repetitions, the target recipientbeing in soft handoff; and wherein if the number of paging repetitionsis one, transmitting a paging message to the target recipient during anext transmission slot assigned to the target recipient.
 2. The methodas in claim 1, further comprising: determining a loading condition ofthe base station; and transmitting a paging message to the targetrecipient within the number of paging repetitions.
 3. In a wirelesscommunication system having a base station controller and a plurality ofbase stations, a base station, comprising: means for receiving a paginginstruction from the base station controller at a base station of theplurality of base stations, the paging instruction specifying a numberof paging repetitions; means for transmitting a quick paging message toa target recipient of the paging instruction for the number of pagingrepetitions, wherein the target recipient is in soft handoff; andwherein if the number of paging repetitions is one, transmitting apaging message to the target recipient during a next transmission slotassigned to the target recipient.
 4. The base station as in claim 3,further comprising: means for determining a loading condition of thebase station; and means for transmitting a paging message to the targetrecipient within the number of paging repetitions.
 5. A method for awireless communication system, comprising: receiving a paginginstruction specifying a number of paging repetitions for a targetrecipient in soft handoff with a base station; determining a loadingcondition of the base station; transmitting a quick paging message tothe target recipient during a first and successive time slots until thenumber of paging repetitions are exhausted and the loading condition ofthe base station is below a loading condition threshold.